2001 GTX RFI RPM Issue

[etemplet]

Hi, I've been working on a problem with the RFI. The engine has serious problems in the 4130-4230RPM Range. Feels like a rev limiter. This noise it is making is akin to vroom vroom vroom vroom and it doesn't speed up and stays consistent. After several minutes of playing with the throttle and making my own waves to unload the prop, I can get the engine past this range and it TAKES OFF. Top RPM is 6890-6900 RPM. If I let the RPM drop below 4200 it will do the same thing again consistently.

On a carburated ski I'd look at the rave valves not opening because the range is spot on and the reaction is similar. I'm thinking I have an electrical issue and it could be the MPEM since it controls the rev limiter. I'm gonna do more testing on the rave solenoid. Maybe if the computer does not sense the rave solenoid is working it may limit the engine RPM... who knows. This would be kinda fun but I got other skis arguing with me as well. LOL

Help is appreciated.

 

[etemplet]

Hmmm..... wondering if there is a safe mode if the MPEM detects an issue where it limits the RPM to the 4200 RPM range. I'm not getting any codes but my Candoo doesn't play nice on this particular ski. I wonder if I need to unplug the INFO gauge. Hmmmmm.... Oh I'm gonna be fondling this girl next week.

 

[mikidymac]

How about AC voltage from a bad rectifier causing strange behavior?

 

[etemplet]

Yes sir.

 

[rcgop]

Are you saying that fixed it? I'm having a similar issue. Does unplugging the rectifier make it go away?

 

[etemplet]

Ski has a new rectifier. That's generally the first thing I replace on RFIs. I also checked every electronic component. I replaced the fuel pump module because the regulator was not holding pressure. None of that solved this particular problem. I'm pretty sure I went through the rave valves on this ski and I also tested the check valve from the engine to the rave solenoid. As Mr. Spock so aptly stated on "Star Trek", "If we don't know where it is we need to find out where it isn't." I did get another 2mph out of the ski so far. Ha ha.

What it your ski doing maybe I can help?

 

[rcgop]

Pretty much the same thing you said in the first paragraph of the post. I replaced throttle position sensor and picked up 1 mph, but that ultimately didn't fix it. Rebuilt Raves, replaced check valve, tested solenoid. Tested rectifier and appears to be normal but not confident. The problem is clearly worse under load. Pulling a tube or 3 people on ski causes more delay between 4000-4400. But at 4500 rpm it takes off. Thoughts? Thanks for the help!

 

[etemplet]

Before I replaced the rectifier with a new one, the ski simply powered through this range. Only when held at steady throttle at 4500 could I notice a slight RPM variance. I'm gonna swap Rectifiers.

 

[etemplet]

I rode the ski last week for a bit to try it out. I had the same issue at the same RPM. When I got home I realized i had the Rectifier unplugged so I rode it that way, unknowingly. What I'm going to do now is start from the beginning with the small stuff. I'm gonna replace the spark plugs and check the coils. Make sure the battery is fully charged. It is easy in the troubleshooting process to look past the simple stuff.

I spent a good bit of time checking the rave solenoid (electrical and mechanical operation), rave air lines, rave valves. As mentioned this ski does the same thing with a completely different fuel module. I had the fuel injectors serviced but I'm not ruling out one might have issues. I'll post my findings. Hope all this helps someone. Ha ha.

 

[alkiseadoo]

I just upgraded the rectifier on my sons RFI with one from seadooparts source.com, they have an upgrade model. I installed it but didn't have time to run it before winterization. In our case he would run it for like 3 days at our lake place and then it would need a battery charge. Worth a shot it's like $85 bucks

 

[etemplet]

Well I will now replace the computer from another GTX RFI and give this ski a go. I mentioned that it really felt like a rev limiter issue. I discussed with another individual the location of the rev-limiter but it is on the circuit board it seems. I hate that one day I may have to become more familiar with the printed circuit boards. LOL Point is that NOW... I have a whole nuther computer and if it works that will have solved the problem. If NOT.... well it should be something less expensive which is cool with me. LOL This is a pretty fast GTX !! Fun to ride.

 

[etemplet]

Well I swapped computers and she fired up. Gonna take her to the river tomorrow along with ugly. My 2000 RX Carb version.

 

[etemplet]

Well riding race bikes certainly helped me diagnose this issue but I wasn't sure. It was the rev limiter in the computer obviously. Swapped the computer and no issues at all. I'd like to take the computer apart or at least identify which component houses the rev limiter. Perhaps I can fix this like I did the MPEM on the 1996 SPI. Ski did Great !! 6900 RPM... Wow !! I"m liking that. I'm motivated !! I'm definitely rejetting the carbs on my 1996 787 GTX.